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tarfs: Fix checksum calculation.

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The checksum code assumed that struct ustar_header filled an entire
block and calculcated the checksum based on the size of the structure.
The header is in fact only 500 bytes long while the checksum covers
the entire block (“logical record” in POSIX terms).  Add padding and
an assertion, and clean up the checksum code.

MFC after:	3 days
Sponsored by:	Juniper Networks, Inc.
Sponsored by:	Klara, Inc.
Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D44226
This commit is contained in:
Dag-Erling Smørgrav 2024-03-06 17:14:01 +01:00
parent e212f0c066
commit 0118b0c8e5
2 changed files with 42 additions and 11 deletions
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31
sys/fs/tarfs/tarfs_vfsops.c
View file

@ -56,7 +56,7 @@
#include <fs/tarfs/tarfs.h>
#include <fs/tarfs/tarfs_dbg.h>
CTASSERT(ZERO_REGION_SIZE > TARFS_BLOCKSIZE);
CTASSERT(ZERO_REGION_SIZE >= TARFS_BLOCKSIZE);
struct ustar_header {
char name[100]; /* File name */
@ -75,8 +75,11 @@ struct ustar_header {
char major[8]; /* Device major number */
char minor[8]; /* Device minor number */
char prefix[155]; /* Path prefix */
char _pad[12];
};
CTASSERT(sizeof(struct ustar_header) == TARFS_BLOCKSIZE);
#define TAR_EOF ((off_t)-1)
#define TAR_TYPE_FILE '0'
@ -202,22 +205,27 @@ static boolean_t
tarfs_checksum(struct ustar_header *hdrp)
{
const unsigned char *ptr;
int64_t checksum, hdrsum;
size_t idx;
unsigned long checksum, hdrsum;
hdrsum = tarfs_str2int64(hdrp->checksum, sizeof(hdrp->checksum));
TARFS_DPF(CHECKSUM, "%s: header checksum %lx\n", __func__, hdrsum);
if (tarfs_str2int64(hdrp->checksum, sizeof(hdrp->checksum), &hdrsum) != 0) {
TARFS_DPF(CHECKSUM, "%s: invalid header checksum \"%.*s\"\n",
__func__, (int)sizeof(hdrp->checksum), hdrp->checksum);
return (false);
}
TARFS_DPF(CHECKSUM, "%s: header checksum \"%.*s\" = %#lo\n", __func__,
(int)sizeof(hdrp->checksum), hdrp->checksum, hdrsum);
checksum = 0;
for (ptr = (const unsigned char *)hdrp;
ptr < (const unsigned char *)hdrp->checksum; ptr++)
checksum += *ptr;
for (idx = 0; idx < sizeof(hdrp->checksum); idx++)
for (;
ptr < (const unsigned char *)hdrp->typeflag; ptr++)
checksum += 0x20;
for (ptr = (const unsigned char *)hdrp->typeflag;
for (;
ptr < (const unsigned char *)(hdrp + 1); ptr++)
checksum += *ptr;
TARFS_DPF(CHECKSUM, "%s: calc unsigned checksum %lx\n", __func__,
TARFS_DPF(CHECKSUM, "%s: calc unsigned checksum %#lo\n", __func__,
checksum);
if (hdrsum == checksum)
return (true);
@ -230,12 +238,13 @@ tarfs_checksum(struct ustar_header *hdrp)
for (ptr = (const unsigned char *)hdrp;
ptr < (const unsigned char *)&hdrp->checksum; ptr++)
checksum += *((const signed char *)ptr);
for (idx = 0; idx < sizeof(hdrp->checksum); idx++)
for (;
ptr < (const unsigned char *)&hdrp->typeflag; ptr++)
checksum += 0x20;
for (ptr = (const unsigned char *)&hdrp->typeflag;
for (;
ptr < (const unsigned char *)(hdrp + 1); ptr++)
checksum += *((const signed char *)ptr);
TARFS_DPF(CHECKSUM, "%s: calc signed checksum %lx\n", __func__,
TARFS_DPF(CHECKSUM, "%s: calc signed checksum %#lo\n", __func__,
checksum);
if (hdrsum == checksum)
return (true);

22
tests/sys/fs/tarfs/tarfs_test.sh
View file

@ -285,6 +285,27 @@ tarfs_linktononexistent_body() {
mount -rt tarfs tarfs_linktononexistent.tar "${mnt}"
}
tarfs_linktononexistent_cleanup() {
tarfs_cleanup
}
atf_test_case tarfs_checksum cleanup
tarfs_checksum_head() {
atf_set "descr" "Verify that the checksum covers header padding"
atf_set "require.user" "root"
}
tarfs_checksum_body() {
kldload -n tarfs || atf_skip "This test requires tarfs and could not load it"
mkdir "${mnt}"
touch f
tar -cf tarfs_checksum.tar f
truncate -s 500 tarfs_checksum.tar
printf "\1\1\1\1\1\1\1\1\1\1\1\1" >> tarfs_checksum.tar
dd if=/dev/zero bs=512 count=2 >> tarfs_checksum.tar
hexdump -C tarfs_checksum.tar
atf_check -s not-exit:0 -e match:"Invalid" \
mount -rt tarfs tarfs_checksum.tar "${mnt}"
}
tarfs_checksum_cleanup() {
umount "${mnt}" || true
}
@ -302,4 +323,5 @@ atf_init_test_cases() {
atf_add_test_case tarfs_emptylink
atf_add_test_case tarfs_linktodir
atf_add_test_case tarfs_linktononexistent
atf_add_test_case tarfs_checksum
}